Power metal oxide semiconductor field effect transistor (MOSFET) devices are transistors specifically arranged to operate with high voltages from drain to source (high breakdown voltage BVds) and to carry currents and provide voltage from a voltage supply to a load. A power MOSFET can operate safely with tens or hundreds of volts from drain to source in the off state. Power MOSFETs are manufactured to have relatively low on-resistance so that when the device is active and operating to carry current, the voltages at the drain and source are very close to one another, and the power from the voltage supply at the source of the power MOSFET is efficiently coupled to the output terminal at the drain of the power MOSFET. Vertical devices such as VMOS devices and double-diffused devices such as DMOS transistors can be used as power MOSFETs. Lateral low resistance transistors such as LDMOS transistors can be used as power MOSFETs. The power MOSFET devices are physically larger than logic or control circuit transistors on an integrated circuit, because those devices do not carry current to the load and can be made much smaller. In switched power systems using power MOSFET transistors to deliver current and voltage to a load, an inrush current or short circuit current causes the power MOSFET to heat. Inrush current can increase when the output terminal supplied by a power MOSFET is temporarily shorted to ground, for example. Over-temperature protection arrangements within an integrated circuit including a power MOSFET device can reduce the current flowing through the power MOSFET device or shut off the power MOSFET to protect the power MOSFET from damage. However, sudden high load current also causes a rapid spike in the MOSFET temperature which can degrade the semiconductor device even after the thermal protection is enabled. In multi-channel power MOSFET devices, such as a multiple channel high side driver (HSD) device, the heat generated at a first MOSFET location on a semiconductor device can spread to an adjoining second MOSFET location on the same semiconductor device, the second MOSFET may experience elevated temperatures resulting in the thermal protection being enabled at the second MOSFET. However, when the thermal event at the first location causes a spike in temperature, the thermal protection at the second site may not act rapidly enough to prevent thermal degradation of the MOSFET at the adjoining, second location.
The repeated occurrence of over-heating has a detrimental effect on the life of the HSD devices. In response to this issue, for HSDs used in automotive systems, the AEC (Automotive Electronic Council) promulgates specification AEC-Q100-012 to address and grade the reliability of “smart” HSD devices containing control circuitry and one or more power MOSFET devices in a single IC. Within the AEC specification, a standard test bench and grading table for HSD devices is published with the highest reliability (grade A) for HSD devices completing more than one million test cycles without device failure and the lowest reliability (grade O) for HSD devices completing less than three hundred test cycles. During a test cycle, the output is coupled to ground repeatedly to determine the reliability of the device.